1. Field of the Invention
The present invention relates to the preparation of tertiary butyl alcohol (TBA) by a process wherein isobutane is oxidized to a mixture of tertiary butyl hydroperoxide (TBHP) and TBA, unreacted isobutane is separated from a TBA/TBHP product fraction, TBA is separated from the resulting TBA/TBHP fraction by distillation, and a stream concentrated in TBHP is returned to the isobutane oxidation zone wherein at the isobutane oxidation conditions the TBHP is converted to TBA with a high degree of selectivity.
2. Description of the Prior Art
It is known to oxidize isobutane in the liquid phase to produce a reaction product mixture mainly comprised of TBHP and TBA. See Winkler, et al. U.S. Pat. No. 2,845,461.
A number of patents deal with the catalytic decomposition of hydroperoxides such as TBHP recovered from isobutane oxidation. A series of patents to Sanderson, et al. describes the use of various catalysts to accomplish the TBHP decomposition to TBA. U.S. Pat. No. 4,992,602 uses a metal phthalocyanine catalyst. U.S. Pat. No. 4,910,349 uses a metal phthalocyanine plus rhenium catalyst, U.S. Pat. No. 4,912,266 uses a metal phthalocyanine plus imidazole catalyst, U.S. Pat. No. 4,912,267 uses a base promoted metal phthalocyanine catalyst, U.S. Pat. No. 4,922,033 uses a bidenate promoted ruthenium catalyst, U.S. Pat. No. 4,922,034 uses a metal porphine catalyst, U.S. Pat. No. 4,922,035 uses a promoted metal phthalocyanine catalyst and U.S. Pat. No. 4,922,036 uses a borate promoted metal phthalocyanine catalyst.
Taylor, et al. U.S. Pat. No. 4,551,553 shows the catalytic decomposition of an organic hydroperoxide such as tertiary butyl hydroperoxide using a binary catalyst composed of a mixture of a ruthenium compound with a chromium compound.
Quin U.S. Pat. No. 2,854,487 discloses a process wherein isopropyl benzene hydroperoxides are catalytically decomposed in the presence of hydrogen and a palladium-supported on activated alumina catalyst.
Grane U.S. Pat. No. 3,474,151 discloses that residual quantities of hydroperoxide contaminants present in tertiary butyl alcohol could be thermally decomposed by heating the contaminated tertiary butyl alcohol at a temperature of 375.degree. to 475.degree. F. for about 1 to 10 minutes.
Grane, et al. U.S. Pat. No. 4,294,999 discloses a process wherein isobutane is oxidized in the presence of a solubilized molybdenum catalyst to provide a mixture of TBA, TBHP, methanol, acetone and other oxygen-containing compounds. The tertiary butyl hydroperoxide is thermally decomposed under pressure at about 280.degree. F. to provide a tertiary butyl alcohol product containing only residual quantities of tertiary butyl hydroperoxide which are then decomposed in accordance with Grane U.S. Pat. No. 3,474,141 by heating the tertiary butyl alcohol at 375.degree. to 475.degree. F. for about 1 to 10 minutes.
Grane, et al. U.S. Pat. No. 4,296,262 discloses a related process wherein isobutane is reacted with oxygen in a reaction zone for a residence time of about 1 to 10 hours at a temperature of about 240.degree. to about 340.degree. F. and a pressure of about 100 to about 1000 psig in the presence of a catalytically effective amount of a soluble molybdenum catalyst. A liquid stream comprising tertiary butyl alcohol is recovered from the reaction mixture and fed to a decomposition zone wherein the tertiary butyl hydroperoxide contained therein is decomposed at 250.degree.-350.degree. F. at a pressure lower than the pressure in the oxidation zone. Worell, et al in U.S. Pat. No. 4,296,263 discloses a related process wherein the feedstock is a mixture of normal butane with isobutane and wherein the oxidation catalyst is a soluble form of chromium, cobalt, nickel, manganese, molybdenum or a mixture thereof.
An article entitled "Metal-Catalyzed Epoxidation of Olefins with Organic Hydroperoxides" by Sheldon, et al., Journal of Catalysts, 31, 427-437 (1979) on pages 30 and 31, reports on the results obtained by the Metal-Catalyzed Decomposition of Tertiary Butyl Hydroperoxide in the absence of an olefin including the decomposition of tertiary butyl hydroperoxide in solution in benzene in the presence of Mo, Ti, W and Cr catalysts to provide tertiary butyl alcohol and oxygen.
The procedures for producing TBA described by prior workers were generally expensive and complicated, and in many cases involved the use of costly and contaminating catalytic materials.